This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Viral infections cause disease in both humans and animals, leading to widespread morbidity, hospitalization and deaths each year. Paramyxoviruses and herpesviruses are both enveloped viruses, requiring a membrane fusion step during the entry of the virus into targeted cells. For many paramyxoviruses, two proteins on the virus surface, the hemagglutinin/neuraminidase (HN) and the fusion (F) protein are responsible for receptor binding and membrane fusion during entry into cells. HN binding to sialic acid receptors is thought to activate the F protein to undergo conformational changes. These conformational changes drive membrane fusion, by bringing the cellular and viral membranes together. However, the mechanisms by which receptor recognition and membrane fusion are coupled remain to be elucidated. For the herpesviruses, three glycoproteins are thought to form the conserved machinery for membrane fusion (the gH, gL and gB proteins), while targeting to specific cells is caused by a glycoprotein that varies between different herpesviruses. We are studying the Epstein-Barr virus (EBV), a gamma-herpesvirus, and are currently working on the entry glycoproteins gB, gH, gL and gp42. For this proposal, we are focusing on the investigation of the paramyxovirus HN/H/G and F protein structures and their interactions, as well as on the structures of the EBV gH/gL, gp42 and gB proteins.